14 or 12 gauge wire in remodel ?

blue_fastbackFebruary 1, 2008

This is a questions for the electricians. When installing new wiring say in a basement remodel or even new construction, do you use 14 gauge anymore or strictly 12 gauge in your outlets and lighting wire?

Just don't put #14 on a circuit fed from a 20A breaker-that requires #12.

A circuit on a 15A breaker can be #14 and as pointed out it is easier to work with. If you have long runs it is beneficial to use #12 on the 15A circuits as there will be less voltage drop (dimming lights when other loads change).

It is highly advisable to use 20A (#12) circuits for bathrooms and to keep each bathroom on its own circuit because of the big loads hair care appliances can take.

The rule is relative simple, use 14 for lighting and 12 for plugs and do not mix them. That keeps the dimming etc at a minimum when large loads start. The breakers protect the wire not the loads so use a 20A for #12 and a 15A for #14. Don't forget to connect all the grounds properly, they protect you. Unless your run is over 150' and has a large load increasing the wire size has virtually no effect, it just costs money, for example 150' of Romex (300' wire) @ 15A will drop 11.5V on #14 and 7.2V on #12, the delta is only 4.3V.

Even with #12 the 7.2 V is 6% of your power going to waste and possible problems starting motors. At the assumed distance of 150 ft, which is longer than most runs in the average house, #14 would be a bad idea for heavy loads and #12 still doesn't quite meet the suggested guideline of 5% drop.

I may have mentioned that I did a service call to the home of a friend that was having a GFCI problem. The home is new and quite large and nice. The individual who wired the home did everything with 12ga on 20 amp circuits. IMO, this is just fine, however, I think 12 ga is a little overkill on light circuits. We even use 14ga 15 amp circuits on some receptacles such as bedrooms where there is little demand. By code, we use 12ga 20 amp circuits on all receptacles in kitchens and dining rooms and others where we think necessary such as garage circuits and GFCI circuits in bathrooms. Why not use all 12 ga? Think we all enjoy wrestling 12 ga wire.

I am using 12 gauge for everything in my addition -- lights and receptacles. We're going to be in this house for the long haul, and I figured in the future I might want to tap into some power for outside lights, or whatever. And even if I don't grab power from a receptacle in the future, I like the thought of a bigger wire taking care of a relatively light load of electricity. Yeah, it's a real pain in the rear trying to pigtail that crap in a box, but I'm happier with it than if I had used 14 gauge.

Guys,, just want say how much I've appreciated this thread. I looked exhaustively for a pros and cons to using 12 AWG vs 14 AWG for all circuits (including standard 15 Amp ones). I was always taught that 14 was for 15 Amp, and 12 was for 20 Amp, but lately I've read about using 12/2, especially for longer runs to compensate for line loss. I'm not so worried about the added cost or even the added difficulty of pulling 12/2, but like most of you, I just hate working with it inside boxes or making pigtails.

I'm building my dream home and just starting on the electrical rough in, so this couldn't have come at a better time. I could see using 12/2 for long runs, and by that I mean typically 70 to 100 feet, but only for receptacles, not lighting.

I live in Ontario Canada, so our electrical code isn't exactly the same as your NEC. If anything, we're usually a little behind the curve (e.g., we still only require AFCIs in new bedrooms where as your NEC requires them in almost every room of a house).

I'm thinking I should probably run 12/2 on 15 Amp breakers on these longer runs, 12/2 on 20 Amp breakers for appliances like fridge, freezer, washer, dishwasher and to all the oulets in my workshop.

Finally, the only point I didn't see mentioned when people argue the "future use" card, is that in our modern society, the trend seems to be moving toward higher efficiency, so I don't think devices of the future should be drawing as much power as they have in recent years. Hopefully these improvements in efficiency should make up for higher usage...

I agree devices are getting more efficient in the way they use energy. However, we are using many more devices than in the past and the new devices are often using more power than earlier models (again, even if they use the added power more efficiently). An example is my wife's stand mixer. The new model is quieter and does not get very hot (efficient use of electricity); but uses about 50% more amps than the old mixer.

I err on the side of more circuits and/or 20 AWG circuits for future requirements.

I ran across this thread while searching for some info about14 and 12 gauge wire, and I was surprised by the different opinions. I'm not an electrician, though I've wired AC and DC circuits since I was a kid. A small bit of basic electromagnetism will help solve some of the things discussed here, I'll make a few points with regard to these wires...

First, the power dissipated in a length or wire is directly proportional to the current squared and its total resistance. Resistance in a wire is directly proportional to the resistivity of the material its made of, the length of wire and inversely proportional to the cross sectional area of the wire. The resistivity of copper is roughly 1.68*10^-8 ohm-meters.

From the description above and due to the conservation of charge and current, I would state that regardless of the load of distance of wire, each foot length of X gauge wire with N amps of current dissipates the same power irregardless of the total length of the wire. So the power used due to the resistance in the wire per unit length is the same no matter how much load is hooked to the wire.

Using the resistance of a wire, you only need Ohms Law to calculate all the other properties described in this thread.

Using a base of 46 meters (roughly 151 ft, SI units are need for easy calculations), I'll show some calculations of voltage drop, etc.

So there it is. Relative to its accepted current limit, 12 gauge has less voltage drop. But 14 ga still is within the NEC standards of You can use some algebra on the formulas above and solve for a maximum length based on a 6 volt drop.